An automated chamber system for measuring soil respiration

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Abstract
To quantify the net effect of agricultural systems on CO2 emissions to the atmosphere, the amount of carbon fixed (primary production) and emitted (soil respiration) under different agronomic management must be estimated. A dynamic chamber system was constructed to automatically measure CO2 concentration in chambers and provide diurnal flux estimates of soil respiration. In fallow, the mean respiration was measured over 4 d using four chambers and ranged from 6.5 to 8.6 g m−2 d−1. During this time, the coefficient of variation between chambers ranged from 9 to 18%. The mean daily soil respiration in fallow was also measured over a second period (13 d) using both chambers and a Bowen ratio technique. The mean value from the chambers was 6.4 g m−2 d−1, which was not significantly (P > 0.05) different from that Bowen ratio value of 7.1 g m−2 d−1. The chambers were also utilized to measure the impact of tillage on soil respiration for 11 d following tillage. During this period, the tilled plot lost 92 kg ha−1 of carbon compared with 52 kg ha−1 from the untilled plot. Approximately half of the total tillage-induced carbon loss from soil occurred in the first 48 h. Key words: Soil respiration, carbon dioxide, soil chamber, tillage, Bowen ratio

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